In buckle folding machines, the paper deflectors, which can be actuated by electromagnetic drive means and restoring springs and are each arranged in front of a folding pocket and can be moved into a corresponding locking position to close the mouth of the folding pocket, consist--because of the usually limited space available between the mouth of the folding pocket, on the one hand, and the folding rollers located in front of it, on the other hand--of relatively thin, rod-shaped profiled parts, which may have, like the folding pockets, a length of 50 cm or more. Therefore, at right angles to their flat side, they have a relatively low flexural strength, which may lead to an insufficient guiding function during the processing of thick or heavy paper or during the processing of a plurality of paper sheets together, if the paper deflector is located in its locking position, in which it closes the mouth of the folding pocket. This insufficient bending strength may lead to excessive sagging of the paper deflector and to jamming of paper.
This disadvantage is also present in a prior-art paper-guiding device of the type mentioned in the introduction (DE 39,30,855 A1), in which the paper deflector has a convex guiding surface on one of its flat sides, and this guiding surface directs, in its resting position, the material arriving for folding into the folding pocket, and the opposite flat side of this paper deflector has a concave guiding surface, which guides the material to be folded past the folding pocket in its locking position. Due to the compact design of this prior-art device, and because the paper deflector performs a three-dimensional turning movement rather than a limited pivoting movement around a stationary axis during changeover from one functional position into the other, only little space is available in terms of cross section for accommodating the paper deflector in such a way as to ensure correct functioning. Therefore, the cross-sectional profile of the paper deflector cannot be designed for a bending strength that would be sufficient for all cases.
To impart higher stability to the paper deflector in its locking position in which it closes the mouth of the folding pocket in a paper-guiding device of the type described above, it has also been suggested that a support rail, which is in functional connection with the switching elements of the paper stop, is in contact with the rear side of the paper deflector when the latter is in the locking position, and is in a starting position located at a spaced location from the paper deflector in the resting position of the paper deflector, be arranged on the side of the paper deflector facing the folding pocket.
Aside from the fact that the guide rail, which is insufficient in itself, is still present in this solution as well, and it does not guarantee sufficient reliability of operation under an extreme load, the combination of the mechanical control and actuating means for the paper deflector with the additional support rail and its actuating means represents a complicated and expensive design, which may involve several sources of malfunction.